Add ap_feet model

This is a model to create some space underneath my AX820-WRT wifi access
point.

src/models/ap_feet.py

@@ -0,0 +1,67 @@
+from pathlib import Path
+
+from build123d import (
+    Align,
+    BuildPart,
+    BuildSketch,
+    GridLocations,
+    Kind,
+    Mode,
+    Rectangle,
+    export_stl,
+    extrude,
+    offset,
+)
+
+block_width = 8
+block_height = 11
+block_depth = 13
+
+
+wall_thickness = 1.5
+beam_thickness = 2
+
+frame_height = block_height + 107
+frame_width = block_width + 78.25
+frame_depth = 1.5
+
+OUTPUT_DIR = Path("out")
+
+
+def block():
+    with BuildPart():
+        with BuildSketch() as frame_plan:
+            perimeter = Rectangle(width=frame_width, height=frame_height)
+            offset(
+                perimeter,
+                -wall_thickness,
+                kind=Kind.INTERSECTION,
+                mode=Mode.SUBTRACT,
+            )
+
+        with BuildSketch() as blocks_plan:
+            with GridLocations(
+                frame_width, frame_height, 2, 2, align=(Align.CENTER, Align.CENTER)
+            ):
+                perimeter = Rectangle(width=block_width, height=block_height)
+                offset(
+                    perimeter,
+                    -wall_thickness,
+                    kind=Kind.INTERSECTION,
+                    mode=Mode.SUBTRACT,
+                )
+
+    blocks = extrude(blocks_plan, amount=block_depth)
+    frame = extrude(frame_plan, amount=frame_depth)
+
+    return blocks + frame
+
+
+def main():
+    part = block()
+
+    export_stl(part, OUTPUT_DIR / "ap_feet.stl")
+
+
+if __name__ == "__main__":
+    main()